Along with the cost decrease for establishment of wireless local area network (LAN), there is no computer maker who doesn't try introducing the wireless LAN equipments, for example a wireless net card, into a notebook computer, however a difficult job for antenna design due to the limited space inside the notebook computer.
A U.S. Pat. No. 6,344,823 “Structure of an antenna and method for manufacturing the same” has disclosed a planar inverted F antenna for use in wireless LAN, which is more advantageous than an average single-pole antenna in build-in allocation and convenience for application.
Another U.S. Pat. No. 6,724,348 “Computer with an embedded antenna” has disclosed a planar inverted F antenna for notebook computer by using an LCD as an allocation environment. However, as the radiant gain of a usual planar inverted F antenna is about 2 dBi, the valid transmission range is decreased owing to the space complexity.
A loop antenna is generally applied for high frequency (HF) communication, but rarely used in small communication equipments because of its high input impedance. A U.S. Pat. No. 6,236,368 “Loop antenna assembly for telecommunication devices” has introduced the concept for using loop antenna in small communication equipments, however, in which a defect is that an operating frequency in the range of 0.05–0.3 wavelength is reserved between a loop antenna and a ground plane.
Another U.S. Pat. No. 6,525,694 “High gain printed loop antenna” has disclosed a tip for solving matching problems by means of feeding a web design, however, which is rather overcomplicated in operating two extra loop circuits in parallel, and has a relatively longer reserved distance about 0.11–0.16 times the wavelength of operating frequency.
Yet, another U.S. Pat. No. 6,697,025 “Antenna apparatus” has disclosed an antenna, which can be folded into a rectangle, is placed in a portable receiver element. This antenna is workable near the ground. However, the radiation element must be folded several times, and the antenna must be grounded or a matching element must be adopted, alternatively.